In general, the invention relates to hydraulic systems used in the operation of heavy equipment. More specifically, the invention relates to a electrohydraulic or hydraulic system used for regulating pressure equalization to alleviate harsh oscillation common in the operation of heavy equipment, including but not limited to backhoes, excavators, skid steer drives, crawler drives, outriggers, and wheel loaders.
In general, construction and other heavy equipment use hydraulic systems to perform digging, loading, craning, and like operations. The speed and direction of these functions are controlled with hydraulic valves. Typically at the end of a moving function, the implement exhibits uncontrolled changes in speed and direction producing an oscillatory motion. For example, in a backhoe, the oscillatory motion occurs when its linkage is brought to a stop following a side-to-side maneuver. This oscillation makes it more difficult for the backhoe operator to return the bucket to a given position. The oscillation is caused when the kinetic energy generated by the backhoe movement is transferred to the hydraulic supply lines connected to the backhoes actuators when stopping. The transferred energy produces a sharp increase (or spike) in fluid pressure. The increased fluid pressure transfers the energy into the hydraulic system and the surrounding vehicle. The energy then returns in the opposite direction through the hydraulic lines and exerts the force into the nonmoving actuators. This transfer of energy continues until it is dispelled as heat, or is dissipated through the oscillation of the equipment and the swelling of the hydraulic lines.
Thus, there is a need for a hydraulic system for reducing the amount of oscillatory motion that occurs when a swinging backhoe or other heavy machinery component is brought to a stop. Further, there is a need for increasing the accuracy of swinging the backhoe or other heavy machinery linkage to a desired location.
One aspect of the present invention provides a hydraulic system for regulating pressure equalization to suppress oscillation in a linkage of heavy equipment. The hydraulic system is comprised of a first and second hydraulic line, a crossover valve in communication with the first and second hydraulic lines, a timing system in communication with the crossover valve, and a motion detector in communication with one of the first or second lines. The motion detector senses linkage or control assembly motion and operatively opens the crossover valve, which remains open as directed by the timing system.
Another aspect of the invention includes a method of operating a hydraulic system to regulate pressure equalization. The method of operation includes restricting directional flow of fluid to a crossover valve. The crossover valve is opened when a predetermined pressure differential is reached in a return hydraulic line when deaccelerating the linkage. The fluid flow between the return hydraulic line and a supply hydraulic line through the open crossover valve is metered for fluid volume. Equalization of a pilot pressure to the crossover valve is then delayed to extend open time of the crossover valve.
In addition, another aspect the invention provides a means for a hydraulic system to regulate pressure equalization. The means includes a check valve for increasing the fluid pressure in a return hydraulic line. Flow control valves allow fluid pressure to be applied to a crossover valve. The crossover valve meters the fluid pressure between the first and second hydraulic lines. Finally, a restrictive means for delaying equalization of the pressure to the crossover valve to extend open time of the crossover valve is provided.
One embodiment of the invention is comprised of a first and second hydraulic lines, a motion detector, and a crossover valve in communication with each of the supply and return hydraulic lines. These components may operate electrically, mechanically, hydraulically, or a combination thereof. The crossover valve does not open during acceleration, and is set to open and allow flow between the supply and return hydraulic lines when a predetermined signal occurs from the motion detector. Fluid flow is then metered between the supply and return hydraulic lines through the crossover valve. A timing system is in communication with the crossover valve to regulate when the crossover valve closes and stops flow between the supply and return hydraulic lines.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiment, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.